1. Field of the Invention
The present invention relates to a method and apparatus for monitoring optical switches, and more specifically, to a method and apparatus for monitoring micro-electro-mechanical (xe2x80x9cMEMSxe2x80x9d) optical switches and cross-connects using a photodetector array.
2. Related Art
Fiber optic technology has dramatically increased the quantity of data that can be carried across various network topologies, including local area networks (xe2x80x9cLANsxe2x80x9d), metropolitan area networks (xe2x80x9cMANsxe2x80x9d), and wide area networks (xe2x80x9cWANsxe2x80x9d). Dense wavelength division multiplexing (xe2x80x9cDWDMxe2x80x9d) allows for the transmission of multiple wavelengths of light along a single fiber optic strand, so that large quantities of data can be multiplexed over the multiple wavelengths and transmitted over the single strand. Optical switches and cross-connects allow data transmitted over a fiber-optic network to be optically switched across multiple pairs of fiber optic cables, without requiring conversion of the optical signals to electric signals. In MEMS-based systems, arrays of microfabricated mirrors are controlled electromechanically to switch light from one or more source optical fibers to one or more destination optical fibers.
While current MEMS-based systems can be used for channel routing in optical switches, cross-connects, and other devices, there presently is lacking a means for passively monitoring the switching state and functionality of such devices. Present monitoring systems require the introduction of additional equipment in existing optical networks, and frequently require the disruption of data flowing through the switch or cross-connect to allow monitoring and/or analysis thereof. For example, in order to determine a fault in an optical switch using current monitoring systems, a transponder is required at one end of the switch to send information back to the data source.
It is known in the art to apply photodetectors to a substrate for the purpose of monitoring activity of a MEMS-based switch. However, such an approach is inefficient, because it requires the addition of circuitry to the switch substrate, thereby reducing the capacity and overall compactness of the switch. Accordingly, what would be desirable, but has not yet been provided, is a method and apparatus for monitoring MEMS-based optical switches and cross-connects.
It is an object of the present invention to provide a method and apparatus for monitoring optical switches and cross-connects using a photodetector array.
It is a further object of the present invention to provide a method and apparatus for monitoring optical switches and cross-connects using a photodetector array attached to a substrate of the switch.
It is another object of the present invention to provide a method and apparatus for monitoring optical switches and cross-connects using a plurality of partial reflectors in the switch to reflect a portion of light transmitted through the switch to a photodetector array.
It is yet another object of the present invention to provide a method and apparatus for monitoring optical switches and cross-connects using a plurality of partial reflectors in the switch to reflect a portion of light through a substrate of the switch to a photodetector array interconnected with the substrate of the switch.
The present invention relates to a method and apparatus for monitoring optical switches and cross-connects, such as MEMS-based optical switches and cross-connects. A plurality of partial reflectors are provided along the optical paths of a switch and associated with one or more switching mirrors to partially reflect a portion of light switched by the mirrors to a photodetector array. The light sensed by the array can be used to passively monitor switching states and/or functionality of the switch without disrupting operation thereof.
In an embodiment of the invention, the photodetector array is bonded to the substrate of the switch using indium bump bonding, solder bonding, epoxy bonding, or other hybridization technique known in the art. A plurality of partial reflectors reflect a portion of light switched by one or more mirrors of the switch through the switch substrate and to the photodetector array for sensing thereby. Processing circuitry can be hybridized to the photodetector array, allowing for on-chip amplification, signal processing, data reception, and recovery functions.